/*
 * Copyright 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.paging

import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.mapNotNull

/**
 * Simple bus implementation thats acts like a ConflatedBroadcastChannel based on StateFlow.
 * * It allows not setting an initial value
 * * Sending duplicate values is allowed
 */
internal class ConflatedEventBus<T : Any>(initialValue: T? = null) {
    private val state = MutableStateFlow(Pair(Int.MIN_VALUE, initialValue))

    val flow = state.mapNotNull { it.second }

    fun send(data: T) {
        state.value = Pair(state.value.first + 1, data)
    }
}
